To get the most out of solar energy, it doesn’t mean that you have to go out and get someone to install solar panels on the roof today. There are many ways we can benefit from the solar power. One is the indirect gain – Trombe Walls.
An indirect-gain passive solar home has its thermal storage between the south-facing windows and the living spaces.
Using a Trombe wall is the most common indirect-gain approach. The wall consists of an 8–16 inch-thick masonry wall on the south side of a house. A single or double layer of glass is mounted about 1 inch or less in front of the wall’s surface. Solar heat is absorbed by the wall’s dark-colored outside surface and stored in the wall’s mass, where it radiates into the living space.
The Trombe wall distributes or releases heat into the home over a period of several hours. Solar heat migrates through the wall, reaching its rear surface in the late afternoon or early evening. When the indoor temperature falls below that of the wall’s surface, heat begins to radiate and transfer into the room. For example, heat travels through a masonry wall at an average rate of 1 hour per inch. Therefore, the heat absorbed on the outside of an 8-inch-thick concrete wall at noon will enter the interior living space around 8 p.m.
Did you know that clear glass transmits up to 90% of solar radiation. It either absorbs or reflects only 10% of solar radiation.You would think since clear glass can transmit solar radiation in, it can also transmit it back. The beauty is that, it doesn’t, after solar radiation is transmitted through the glass and absorbed by the home, it is radiated again from the interior surfaces as infrared radiation.
Although glass allows solar radiation to pass through, it absorbs the infrared radiation. The glass then radiates part of that heat back to the home’s interior. In this way, glass traps solar heat entering the home. So that’s why many energy efficient homes have almost all glass walls or large windows.
With the large window and skylights installed in the house, it’s definitely a great way to harvest solar energy. However, there’s a problem. You will also get the sun light in summer which can heat up the house like an oven. So the energy you saved during winters times are spent in the summer to cool off. However, it doesn’t have to be that way.
All it takes is to block the sunlight in the summer. You can do so by using overhang and shutters. Interior and exterior window shutters can help reduce heat gain in your home. Window shutters also offer weather protection and add more security to your house.
Solar power is the new old technology that people are using to help them save money. With the economy down and prices up, people are looking for new ways to save or even make money, which solar is a good option. With this, you can buy a pre build system that you piece together or you can make your own if you so inclined.
The savings on your electric bill can save you up to 100% of your bill if you get a large enough system. If you build a system that is bigger than you use, you can sell the power back to the electric company for a little bit of profit. This might vary state to state but most states are required to buy your power at market price.
The other plus of solar power is that you save the environment by using the natural power of the sun. If enough people use this way of power, we will all save a lot of money and cut down on carbon, and other emissions pumped into the air by power generation. So help yourself and the earth out and go green. Thank you and use solar power today.
The following five elements constitute a complete passive solar home design. Each performs a separate function, but all five must work together for the design to be successful.
The large glass (window) area through which sunlight enters the building. Typically, the aperture(s) should face within 30 degrees of true south and should not be shaded by other buildings or trees from 9 a.m. to 3 p.m. each day during the heating season.
The hard, darkened surface of the storage element. This surface—which could be that of a masonry wall, floor, or partition (phase change material), or that of a water container—sits in the direct path of sunlight. Sunlight hits the surface and is absorbed as heat.
The materials that retain or store the heat produced by sunlight. The difference between the absorber and thermal mass, although they often form the same wall or floor, is that the absorber is an exposed surface whereas thermal mass is the material below or behind that surface.
The method by which solar heat circulates from the collection and storage points to different areas of the house. A strictly passive design will use the three natural heat transfer modes—conduction, convection, and radiation—exclusively. In some applications, however, fans, ducts, and blowers may help with the distribution of heat through the house.
Roof overhangs can be used to shade the aperture area during summer months. Other elements that control under- and/or overheating include electronic sensing devices, such as a differential thermostat that signals a fan to turn on; operable vents and dampers that allow or restrict heat flow; low-emissivity blinds; and awnings.
Source: EERE, U.S. Department of Energy
To understand how a passive solar home design works, you need to understand how heat moves and how it can be stored.
As a fundamental law, heat moves from warmer materials to cooler ones until there is no longer a temperature difference between the two. To distribute heat throughout the living space, a passive solar home design makes use of this law through the following heat-movement and heat-storage mechanisms:
Conduction is the way heat moves through materials, traveling from molecule to molecule. Heat causes molecules close to the heat source to vibrate vigorously, and these vibrations spread to neighboring molecules, thus transferring heat energy. For example, a spoon placed into a hot cup of coffee conducts heat through its handle and into the hand that grasps it.
Convection is the way heat circulates through liquids and gases. Lighter, warmer fluid rises, and cooler, denser fluid sinks. For instance, warm air rises because it is lighter than cold air, which sinks. This is why warmer air accumulates on the second floor of a house, while the basement stays cool. Some passive solar homes use air convection to carry solar heat from a south wall into the building’s interior.
Radiant heat moves through the air from warmer objects to cooler ones. There are two types of radiation important to passive solar design: solar radiation and infrared radiation. When radiation strikes an object, it is absorbed, reflected, or transmitted, depending on certain properties of that object.
Opaque objects absorb 40%–95% of incoming solar radiation from the sun, depending on their color—darker colors typically absorb a greater percentage than lighter colors. This is why solar-absorber surfaces tend to be dark colored. Bright-white materials or objects reflect 80%–98% of incoming solar energy.
Inside a home, infrared radiation occurs when warmed surfaces radiate heat towards cooler surfaces. For example, your body can radiate infrared heat to a cold surface, possibly causing you discomfort. These surfaces can include walls, windows, or ceilings in the home.
Clear glass transmits 80%–90% of solar radiation, absorbing or reflecting only 10%–20%. After solar radiation is transmitted through the glass and absorbed by the home, it is radiated again from the interior surfaces as infrared radiation. Although glass allows solar radiation to pass through, it absorbs the infrared radiation. The glass then radiates part of that heat back to the home’s interior. In this way, glass traps solar heat entering the home.
Thermal capacitance refers to the ability of materials to store heat. Thermal mass refers to the materials that store heat. Thermal mass stores heat by changing its temperature, which can be done by storing heat from a warm room or by converting direct solar radiation into heat. The more thermal mass, the more heat can be stored for each degree rise in temperature. Masonry materials, like concrete, stones, brick, and tile, are commonly used as thermal mass in passive solar homes. Water also has been successfully used.
Source: EERE, U.S. Department of Energy
Your home’s windows, walls, and floors can be designed to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design or climatic design. Unlike active solar heating systems, passive solar design doesn’t involve the use of mechanical and electrical devices, such as pumps, fans, or electrical controls to move the solar heat.
Passive solar homes range from those heated almost entirely by the sun to those with south-facing windows that provide some fraction of the heating load. The difference between a passive solar home and a conventional home is design. The key is designing a passive solar home to best take advantage of your local climate. For more information, see how a passive solar home design works.
You can apply passive solar design techniques most easily when designing a new home. However, existing buildings can be adapted or “retrofitted” to passively collect and store solar heat.
To design a completely passive solar home, you need to incorporate what are considered the five elements of passive solar design. Other design elements include:
* Window location and glazing type
* Insulation and air sealing
* Auxiliary heating and cooling systems, if needed.
These design elements can be applied using one or more of the following passive solar design techniques:
* Direct gain
* Indirect gain (Trombe wall)
* Isolated gain (Sunspace).
When incorporating these design elements and techniques, you want to design for summer comfort, not just for winter heating.
Your home’s landscaping can also be incorporated into your passive solar design.
Source: EERE, U.S. Department of Energy